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Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?
- From: Andi Kleen <andi at firstfloor dot org>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: Linus Torvalds <torvalds at linux-foundation dot org>, Jim Bos <jim876 at xs4all dot nl>, Andi Kleen <andi at firstfloor dot org>, James Cloos <cloos at jhcloos dot com>, Linux Kernel Mailing List <linux-kernel at vger dot kernel dot org>, Andreas Schwab <schwab at redhat dot com>, Michael Matz <matz at suse dot de>, Dave Korn <dave dot korn dot cygwin at gmail dot com>, Richard Guenther <richard dot guenther at gmail dot com>, gcc at gcc dot gnu dot org
- Date: Mon, 15 Nov 2010 23:43:22 +0100
- Subject: Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?
- References: <20101115105446.GD7269@basil.fritz.box> <20101115111642.GU29412@tyan-ft48-01.lab.bos.redhat.com> <AANLkTi=jwrt2VE5tnL9NR2WhGDnQtv+k6rapnHfsy_aL@mail.gmail.com> <4CE17098.8090000@xs4all.nl> <AANLkTimEw0U5TqMcmoeShXQ67kqp32hp5fwd2oRQhWo2@mail.gmail.com> <4CE17C4B.1070305@xs4all.nl> <20101115185848.GI2583@sunsite.ms.mff.cuni.cz> <20101115191248.GY29412@tyan-ft48-01.lab.bos.redhat.com> <AANLkTikeYLrqXhvTP_uuKnKhy=k7pAQCbONJdKBc838O@mail.gmail.com> <20101115195115.GZ29412@tyan-ft48-01.lab.bos.redhat.com>
> testcase shows that in 4.1/4.2/4.3/4.4 this is miscompiled only when using
> -fno-ipa-reference, in 4.5 it is miscompiled always when optimizing
> unless -fno-ipa-pure-const (as 4.5 added local-pure-const pass which is run
> before ipa-reference) and in 4.6 this has been fixed by Honza when
> doing ipa cleanups.
Maybe it would be better to simply change the kernel Makefiles to pass
-fno-ipa-pure-const instead of adding volatiles everywhere.
-Andi